Submersible pump unit drive heat exchanger having a diaphragm compensator

ABSTRACT

A drive of a submersible pump having a housing, an oil-filled electric motor, a heat exchanger and a compensator hydraulically connected by an oil channel to the oil-filled cavity of the electric motor. The drive has channels to circulate oil in the drive for heat exchange between the oil and the well fluid. Inside the heat exchanger, there is a through channel of the heat exchanger for the well fluid flow. The compensator has a diaphragm placed in a cylindrical casing adjoining an outer side surface of the diaphragm to an inner side surface of the cylindrical casing. The through channel of the heat exchanger for the well fluid flow has an annular cross-section with an inner wall formed by the outer side surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from U.S. provisional patentapplication Ser. No. 63/283,343 filed on 26 Nov. 2021 by Anton Shakirov,et al. and entitled Submersible Pump Unit Drive with Heat Exchanger,which is hereby incorporated by reference in its entirety. This patentapplication claims priority from U.S. patent application Ser. No.17/717,889 filed on Apr. 11, 2022 entitled A METHOD AND APPARATUS FOR ASUBMERSIBLE MULTISTAGE LABYRINTH-SCREW PUMP, which is herebyincorporated by reference herein in its entirety. This patentapplication also claims priority from U.S. Provisional patentapplication Ser. No. 63/298,734 by ANTON Shakirov entitled A METHOD ANDAPPARATUS FOR A SUBMERSIBLE MULTISTAGE LABYRINTH-SCREW PUMP filed onJan. 12, 2022, which is hereby incorporated by reference herein in itsentirety; this patent application also claims priority from U.S.Provisional patent application Ser. No. 63/283,340 by ANTON Shakiroventitled Submersible Oil-filled Permanent Magnet Electric Motor, filedon 26 Nov. 2021, which is hereby incorporated by reference herein in itsentirety; this patent application also claims priority from U.S.Provisional patent application Ser. No. 63/283,342 by ANTON Shakiroventitled Axial Support Shoe Unit of Oil-Filled Submersible Motor filedon 26 Nov. 2021, which is hereby incorporated by reference herein in itsentirety.

BACKGROUND OF THE INVENTION

Downhole high-speed submersible centrifugal pumps are capable ofoperating in conditions where both the pumping mechanical section withstages and the drive part with an electric motor (oil-filled type) arecompletely submerged to a great depth in the well. Such pumps have towork for a long time without maintenance. To do this, in such pumps, thedrive part with an electric motor is made with a heat exchanger andhydraulic protection, consisting of a protector and a compensator.Hydraulic protection is designed to protect submersible oil-filledelectric motors from the penetration of well fluid into their internalcavity, as well as to compensate for oil leakage and thermal changes inits volume during the operation of the electric motor. For the drivepart, it is also necessary to ensure the removal of a significant amountof heat, which is formed as a result of mechanical and electrical lossesin the electric drive of the pump. For this, a dielectric coolant(dielectric oil) is used, which circulates in an electric motor with aheat exchanger. The coolant absorbs heat from the electric motor andtransfers the heat from the electric motor to the surrounding fluid inthe well. Design solutions for the pump drive, which ensure efficientheat removal from electric motors during the operation of the pumpingunit in the well, reduce the likelihood of drive failure, and,accordingly, increase the operating life of the pumping unit as a whole.An increase in the service life of a pumping unit is one of the mainfactors ensuring the stability of oil production and reducing the costof servicing the well stock.

Patent RU No. 2 464 691, published on Oct. 20, 2012 discloses anelectric motor (oil-filled type—with a dielectric liquid (oil)) and aheat exchanger with a compensator installed in the heat exchanger. Theheat exchanger of the electric motor is combined with the compensator insuch a way that the piston of the compensator is located inside theseparating body of the heat exchanger with a hot zone, formed bychannels for the passage of hot oil from the oil-filled electric motor.The disadvantage of this technical solution provided by RU No. 2 464 691is the insufficient efficiency of the heat exchanger, in particular, dueto the presence of only one heat exchange circuit. The disadvantage isthe low efficiency of heat exchange between the electric motor oil beingcooled and the cooling well fluid due to the relatively small area ofthe heat exchange surface over which these fluids flow. As a result, inorder to cool the electric motor oil to a temperature acceptable fromthe point of view of reliable operation of the electric motor, the heatexchanger in this design requires a significant length. In addition, thepiston-type compensator has relatively higher breakaway friction losses(when its internal volume changes with hot oil), which can lead tosignificant pressure drops between the outer and inner cavities of themoving rings. In addition, in the RU No. 2 464 691 design, thecompensator (piston) with elastomeric sealing rings does not havesufficient thermal protection and is close enough to the hot flow zone(with oil)—that this proximity to the hot flow zone leads to an increasein the likelihood of thermal damage to the compensator (in particular,its part made of elastomeric rings).

FIELD OF THE INVENTION

A particular illustrative embodiment of the invention relates toequipment for oil production and can be used in downhole multistagecentrifugal pumps with high-speed drives, built on the basis of anoil-filled electric motor with a heat exchanger, hydraulic protection,and a compensator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a side view of a schematic representation of a drivesubmersible pumping unit with a heat exchanger located in the well; and

FIG. 2 depicts a side view of a schematic representation of a heatexchanger with an installed diaphragm compensator.

SUMMARY OF THE INVENTION

A drive of a submersible pump having a housing, an oil-filled electricmotor, a heat exchanger and a compensator hydraulically connected by anoil channel to the oil-filled cavity of the electric motor. The drivehas channels to circulate oil in the drive for heat exchange between theoil and the well fluid. Inside the heat exchanger, there is a throughchannel of the heat exchanger for the well fluid flow. The compensatorhas a diaphragm placed in a cylindrical casing adjoining the outer sidesurface of the diaphragm to the inner side surface of the cylindricalcasing. The through channel of the heat exchanger for the well fluidflow has an annular cross-section with an inner wall formed by the outerside surface of the above cylindrical casing and with an outer wallformed by the inner surface of the cylindrical sleeve of the heatexchanger.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT OF THE INVENTION

The specification and drawings are to be regarded in an illustrativerather than a restrictive sense. It will be evident that additions,subtractions, deletions, and other modifications and changes may be madethereunto without departing from the broader spirit and scope of theinventions as set forth in the claims set forth below. Accordingly, theinventions are therefore to be limited only by the scope of the appendedclaims. None of the claim language should be interpreted pursuant to 35U.S.C. 112(f) unless the word “means” is recited in any of the claimlanguage, and then only with respect to any recited “means” limitation.The drawings are drawn to scale.

In a particular illustrative embodiment of the invention, a submersiblepump unit drive with a heat exchanger is disclosed. In a particularillustrative embodiment of the invention, the submersible pump unitdrive with heat exchanger improves the design of a drive of asubmersible pumping unit with an oil-filled electric motor and a heatexchanger, which is used in borehole multistage centrifugal pumps. Thisimprovement is aimed at improving the reliability of the pump drive fora longer working life duration and is especially important forhigh-speed submersible pumping units with a valve drive operating atgreat depths with a high temperature of the well fluid.

In a particular illustrative embodiment of the invention, the inventionincreases the service life of an electric drive with a heat exchanger byincreasing the efficiency of heat removal from an oil-filled drive motorwhile reducing the likelihood of thermal damage to the compensator(especially its elastomeric elements) associated with prolonged thermalhigh-temperature exposure to it. An additional advantage of thistechnical solution is the possibility of reducing the length of thedrive by increasing the compactness of the heat exchanger (reducing thelength of the heat exchanger) while reducing the likelihood of thermaldamage to the compensator.

To achieve the claimed technical result in a known drive of asubmersible pumping unit with a heat exchanger containing a housing, anoil-filled electric motor, a heat exchanger attached to it, locatedbelow the electric motor, a compensator installed in the heat exchangerand hydraulically connected by an oil channel with an oil-filled cavityof the electric motor, channels providing oil circulation in the drivefor heat exchange between oil and well fluid, a through channel of theheat exchanger is provided inside of the heat exchanger for the flow ofwell fluid. The heat exchanger has an inlet for the flow of well fluidfrom the annulus into the heat exchanger and an outlet for the flow ofthe well fluid out of the heat exchanger and into the annulus. The inletand outlet of the heat exchanger are provided respectively in the lowerand upper parts of the heat exchanger. In a particular illustrativeembodiment of the invention, the compensator has a diaphragm made ofelastomeric material, which is placed in a cylindrical casing made ofheat-conducting material adjoining the outer side surface of thediaphragm to a corresponding inner side surface of the cylindricalcasing.

The above through channel of the heat exchanger for the flow of wellfluid is a channel of an annular cross-section with an inner wall formedby an outside surface of the above cylindrical casing and with an outerwall formed by the inside surface of the cylindrical sleeve of the heatexchanger. The heat exchanger comprises a circulation channel for oilfrom the electric motor for heat exchange between oil and well fluid,formed between the outer surface of the heat exchanger sleeve and theinner surface of the heat exchanger housing. In a particularillustrative embodiment of the invention, the diaphragm is made in theform of a two-bag diaphragm, and the heat exchanger has lower and upperflanges, in which the inlet and outlet of the through channel of theinner contour of the heat exchanger for the well fluid flow are made,respectively.

Turning now to FIG. 1 , in a particular illustrative embodiment of theinvention, a drive of a submersible pumping unit with a heat exchangercontains an electric motor 1 filled with a dielectric liquid (protector(not specified)) is located above the electric motor), a heat exchanger2 attached to the electric motor from below with a built-in compensator12. The drive is placed in the well (see FIG. 1 ) and surroundeddownhole fluid in the annulus 36 (a predominantly annular space betweenthe outer surface of the submersible part of the pumping unit and thewalls of the well).

A double-circuit heat exchanger with a compensator is attached to thepower section (electric motor section) using a mounting flange 3 to thepower section, studs 5, nuts 6. The double-circuit heat exchanger (alsoreferred to as “heat exchanger” in the description of an illustrativeembodiment of the invention) contains oil channels 25, 26 separated by abushing 4. The double-circuit heat exchanger 2 with a compensatorcontains an upper flange 7, a lower flange 16, a body 8, and a heatexchanger sleeve 10. Sleeve 10 can be made of metal with a helical wirewinding of its outer surface to intensify heat exchange processes—if itsouter surface forms part of the surface of the oil channel (with flowdirection 24).

In a particular illustrative embodiment of the invention, a compensatorwith a compensator diaphragm in the form of a first bag (diaphragm) 12and a second bag (diaphragm) 40 is attached using bushings 9, 14 and 27and sleeves 11. The compensator diaphragm is elongated in the verticaldirection and is preferably made of an elastomeric material. The outersurface of the compensator is limited by a rigid cylindrical casing 13made of a heat-conducting material (usually made of metal) mounted on amount 15. In the flanges 7 and 16, oil inlet and outlet sections (alsoreferred to herein as “channels”) 19 and 20 are provided for providing acirculation channel for oil thereby enabling a circulation flow in thedirection of the oil flow 24 (downward) of a motor for heat exchangebetween oil and well fluid formed between the outer surface of the heatexchanger sleeve 10 and the inner surface of the heat exchanger body 8.Such a passage preferably has an annular cross-section.

Also, in the flanges 7 and 16 an outlet channel opening and an inletchannel opening are provided for supplying fluid output to the throughchannel for the well fluid in the heat exchanger, respectively, for theflow of the well fluid 17 and 18 (the outlet and inlet of the well fluidflow from the annulus 36). The direction of the well fluid flows isindicated by arrows 21, 22, the direction of the oil flows 23 and 24.Rubber rings 28, 29, 30, 31, 32 and 33 are provided to seal the internalcavity of the electric motor and rings 35 are used to separate the oilflows.

In a particular illustrative embodiment of the invention, the deviceworks as follows. The oil in the motor absorbs the heat from the runningmotor and conducts the absorbed heat to the well fluid. Oil flowsthrough the electric motor and the heat exchanger. Namely, oil(dielectric coolant) from the motor circulates through channels (oillines) circulating oil in the drive for heat exchange between oil andwell fluid (for example, an oil circulating pump). The oil circulationis ensured, in particular, by an inlet channel 19 connected to theoil-filled cavity of the engine and ensuring the flow of oil into theannular channel for oil circulation in the direction 24 through the heatexchanger. Oil channel 26 also provides the operation of a compensatorwith a diaphragm containing additional dielectric oil in its internalcavity to compensate for the thermal expansion of oil in the motorcavity (and to compensate for the inevitable oil leakage from theoil-filled zone of the electric motor).

In the through channel of the heat exchanger (part of the internalcontour of the heat exchanger) for the flow of well fluid through theinlet 18 (channel in the flange), well fluid from the annulus with wellfluid 36 enters. With a wall formed by the outer side surface of thecylindrical casing 13 and with an outer wall formed by the inner surfaceof the cylindrical sleeve of the heat exchanger 10. This flowsimultaneously provides: cooling of the compensator with first bag(diaphragm) 12 (through a thin-walled (for example, less than 2 mmthick) cylindrical steel casing 13), and a second bag or diaphragm 40,wherein such cooling prolongs the life of the diaphragm compensator.

In a particular illustrative embodiment of the invention, the diaphragmis made of an elastomeric material (rubber type), creating a morefavorable temperature regime for the diaphragm. Thermal insulation ofthe compensator from the hot zone is provided by the circulation channelfor oil from the electric motor for heat exchange between oil from theelectric motor and the well fluid, formed between the outer surface ofthe heat exchanger sleeve 10 and the inner surface of the heat exchangerhousing 8, which also creates a more favorable temperature regime forthe diaphragm—primarily for its elastomeric elements (bag (diaphragm)).A particular illustrative embodiment of the invention contributes to thecooling of the above oil circulation path (with flow 24) from theelectric motor for heat exchange between the oil and the well fluid.

In a particular illustrative embodiment of the invention, the creationof such a second (internal) circuit with a through channel for the flowof well fluid in the heat exchanger) can increase the heat exchangesurface by almost 2 times while maintaining the length of the heatexchanger.

In a primary (outer) loop, the passing oil flow in direction 24 in theoil circulation path from the electric motor for heat exchange betweenoil and well fluid (formed between the sleeve and the heat exchangerhousing) is also cooled by the well fluid flow in the annulus indirection 21 (i.e. in the opposite direction to the well fluid flow).

In a particular illustrative embodiment of the invention, location ofthe motor heat exchanger below the motor may be advantageous when thepumping unit is located in the wellbore above the zone of perforations(′perforations' may be provided in the casing at desired locations toallow formation fluids to enter the casing). With this arrangement, thefluid drawn into the wellbore passes, in particular, over the outside ofthe heat exchanger before it is heated by the engine. This contributesto the more efficient operation of the heat exchanger.

In a particular illustrative embodiment of the invention, the term“forced cooling system” refers to the double-circuit heat exchangers(also referred to herein as heat exchanger having a “two-bag” or“double-bag” diaphragm compensator) described herein and is preferredbecause of the small size of the power unit and intense heat generationwithin it. In such a system, an efficient heat exchanger and thecreation of an intensive circulation of flows (oil and well fluid)through it are always preferred. Since this design reduces the amount ofoil (when using a single bag compensator 12) that heats up and expandswhen the motor is running, a larger oil volume compensator (double bag(diaphragm) compensator, a first bag (diaphragm) 12 and a second bag(diaphragm) 40) is preferred. Therefore, it is highly desirable to makethe compensator as a two-bag compensator, in which the design of theconnection of the bags provides for the minimum size of the product.

In a particular illustrative embodiment of the invention, adouble-circuit heat exchanger with a compensator is made of pipes with acalculated length corresponding to a required cooling of the power unitor motor when operating in the nominal mode. All the main structuralelements of the heat exchanger, except for the compensator diaphragm, inparticular, the lower 16 and upper flanges 7, the cylindrical casing 13,the cylindrical sleeve of the heat exchanger 10, the cylindrical casing8 can be made of steel—in particular, carbon steel or (forcorrosion-resistant design) stainless steel.

In a particular illustrative embodiment of the invention, the typicalthickness of the cylindrical sleeve 10 is from 2 mm to 6.5 mm, thetypical thickness of the cylindrical casing 13 is from—0.5 to 2 mm, thetypical thickness of the housing 8—from 4 to 7 mm. The range of outsidediameters of the housing 8 is for example, from 103 mm to 185 mm.Diameters of input and output channels 7.18— from 3 to 15 mm. Thetypical thickness range of the oil pipeline flow channel is from 1.5 to3 mm.

The location of the motor heat exchanger below the motor may beadvantageous in applications where the pumping unit is located in thewellbore above the zone of perforations (′perforations' may be providedin the casing at desired locations to allow formation fluids to enterthe casing). With this arrangement, the fluid drawn into the wellborepasses, in particular, over the outside of the heat exchanger before itis heated by the motor. In a particular illustrative embodiment of theinvention, a water protector is placed above the motor. In other cases,the use of the use of forced flow casing is preferred.

In a particular illustrative embodiment of the invention, a submersiblepump unit drive with heat exchanger is disclosed, comprising a housing;an oil-filled electric motor contained in the housing; a heat exchangerconnected to the electric motor and located below the electric motor; acompensator installed in the heat exchanger; an oil channelhydraulically connected with an oil-filled cavity in the electric motor,wherein the oil channel provides oil circulation in the electric motorfor heat exchange between oil and well fluid; a through channel insideof the heat exchanger for flow of well fluid through the heat exchanger,wherein the through channel has an inlet for flow of well fluid from anannulus and an outlet for the flow of well fluid into the annulus,wherein the inlet and the outlet are made in an lower and upper parts ofthe heat exchanger respectively; a diaphragm made of elastomericmaterial, which is placed in a cylindrical casing adjoining an outerside surface of the diaphragm to a corresponding inside surface of anoutside surface of the cylindrical casing; and a cylindrical sleevesurrounding the cylindrical casing of the heat exchanger wherein thethrough channel of the heat exchanger for the flow of the well fluid isa channel of an annular cross section with an inner wall formed by anouter surface of the cylindrical casing and with an outer wall formed byan inner surface of the cylindrical sleeve of the heat exchanger, whilethe heat exchanger contains a circulation channel for oil from theelectric motor for heat exchange between oil and well fluid, formedbetween the outer surface of the heat exchanger sleeve and the innersurface of the heat exchanger housing.

In another particular illustrative embodiment of the invention thediaphragm further comprises a two-bag diaphragm, and wherein the heatexchanger has lower and upper flanges, in which the inlet and outlet ofthe through channel of the heat exchanger are made, respectively, forthe flow of well fluid, wherein the two-bag diaphragm is placed in acylindrical casing between a first flange and a second flange. In aparticular illustrative embodiment of the invention, a submersible pumpunit drive with a heat exchanger is disclosed, comprising a housing; anoil-filled electric motor contained in the housing; a heat exchangerconnected to the electric motor and located below the electric motor; acompensator installed in the heat exchanger; an oil channelhydraulically connected with an oil-filled cavity in the electric motor,wherein the oil channel provides oil circulation in the electric motorfor heat exchange between the oil in oil-filled cavity in the electricmotor and well fluid; and a through channel inside of the heat exchangerfor a flow of the well fluid through the heat exchanger, wherein thethrough channel has an inlet for flow of well fluid from an annulus andan outlet for the flow of well fluid into the annulus, wherein the inletand the outlet are made in a lower and upper part of the heat exchangerrespectively.

In another particular illustrative embodiment of the invention thesubmersible pump unit drive further comprises a two-bag diaphragm madeof elastomeric material, which is placed in a cylindrical casingadjoining an outer side surface of the diaphragm to a correspondinginside surface of an outside surface of the cylindrical casing.

In another particular illustrative embodiment of the invention thesubmersible pump unit drive further comprises, a cylindrical sleevesurrounding the cylindrical casing of the heat exchanger wherein thethrough channel of the heat exchanger for the flow of the well fluid isa channel of an annular cross section with an inner wall formed by anouter surface of the cylindrical casing and with an outer wall formed byan inner surface of the cylindrical sleeve of the heat exchanger, whilethe heat exchanger contains a circulation channel for oil from theelectric motor for heat exchange between oil and well fluid, formedbetween an outer surface of the heat exchanger cylindrical sleeve andthe inner surface of the heat exchanger housing.

In another particular illustrative embodiment of the invention thesubmersible pump unit drive further comprises a method for cooling asubmersible pump unit drive, the method comprising circulating oil in anoil-filled electric motor contained in a submersible pump unit drivethrough an oil channel hydraulically connected with an oil-filled cavityin the electric motor, wherein the oil channel provides oil circulationin the electric motor between the electric motor and a heat exchangerfor heat exchange between the oil and a well fluid.

In another particular illustrative embodiment of the invention themethod for cooling a submersible pump unit drive further comprises,flowing well fluid through channel inside of the heat exchanger for flowof well fluid through the heat exchanger, wherein the through channelhas an inlet for flow of well fluid from an annulus and an outlet forthe flow of well fluid into the annulus, wherein the inlet and theoutlet are made in a lower and upper part of the heat exchangerrespectively.

In another particular illustrative embodiment of the invention themethod for cooling a submersible pump unit drive, a first diaphragm madeof elastomeric material, which is placed in a cylindrical casingadjoining an outer side surface of the diaphragm to a correspondinginside surface of an outside surface of the cylindrical casing.

In another particular illustrative embodiment of the invention themethod for cooling a submersible pump unit drive, a cylindrical sleevesurrounding the cylindrical casing of the heat exchanger wherein thethrough channel of the heat exchanger for a flow of the well fluid is achannel of an annular cross section with an inner wall formed by anouter surface of the cylindrical casing and with an outer wall formed byan inner surface of the cylindrical sleeve of the heat exchanger, whilethe heat exchanger contains a circulation channel for oil from theelectric motor for heat exchange between oil and well fluid, formedbetween the outer surface of the heat exchanger sleeve and the innersurface of a heat exchanger housing.

In another particular illustrative embodiment of the invention themethod for cooling a submersible pump unit drive, a second diaphragmmade of elastomeric material, is placed in a cylindrical casingadjoining an outer side surface of the diaphragm to a correspondinginside surface of an outside surface of a cylindrical casing.

In a particular illustrative embodiment of the invention, the drive withthe specified heat exchanger provides an increase in heat transfer. Itprovides an increased rate of heat transfer along the internal contour.The use of an electric drive of a submersible pump with such a heatexchanger provides an increase in the compactness of the heat exchangerfor a submersible oil-filled electric motor and effective maintenance ofa given operating temperature range of an oil-filled electric motor,which ultimately prolongs the service life of the pumping unit.

1. A submersible pump unit drive with heat exchanger, comprising: a housing; an oil-filled electric motor contained in the housing; a heat exchanger connected to the electric motor and located below the electric motor; a compensator installed in the heat exchanger; an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor for heat exchange between oil and well fluid; a through channel inside of the heat exchanger for flow of well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in an lower and upper parts of the heat exchanger respectively.
 2. The submersible pump unit drive with heat exchanger of claim 1, further comprising: a diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing.
 3. The submersible pump unit drive with heat exchanger of claim 2, further comprising: a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for the flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between the outer surface of the heat exchanger sleeve and the inner surface of the heat exchanger housing.
 4. The submersible pump unit drive of claim 3, wherein the diaphragm further comprises a two-bag diaphragm, and wherein the heat exchanger has lower and upper flanges, in which the inlet and outlet of the through channel of the heat exchanger are made, respectively, for the flow of well fluid, wherein the two-bag diaphragm is placed in a cylindrical casing between a first flange and a second flange.
 5. A submersible pump unit drive with a heat exchanger, comprising: a housing; an oil-filled electric motor contained in the housing; a heat exchanger connected to the electric motor and located below the electric motor; a compensator installed in the heat exchanger; an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor for heat exchange between the oil in oil-filled cavity in the electric motor and well fluid; and a through channel inside of the heat exchanger for a flow of the well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in a lower and upper part of the heat exchanger respectively.
 6. The submersible pump unit drive of claim 5, further comprising: a two-bag diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing.
 7. The submersible pump unit drive of claim 6, further comprising: a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for the flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between an outer surface of the heat exchanger cylindrical sleeve and the inner surface of the heat exchanger housing.
 8. A method for cooling a submersible pump unit drive, the method comprising: circulating oil in an oil-filled electric motor contained in a submersible pump unit drive through an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor between the electric motor and a heat exchanger for heat exchange between the oil and a well fluid.
 9. The method of claim 8, the method further comprising: flowing well fluid through channel inside of the heat exchanger for flow of well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in a lower and upper part of the heat exchanger respectively.
 10. The method of claim 9, wherein a first diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing.
 11. The method of claim 10, wherein a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for a flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between the outer surface of the heat exchanger sleeve and the inner surface of a heat exchanger housing.
 12. The method of claim 11 wherein a second diaphragm made of elastomeric material, is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of a cylindrical casing. 